It is known to provide fastening systems that include threaded inserts of metal that are anchored in plastic or other components when used to receive a screw or bolt for holding a second component in an assembly. For example, plastic parts in automobiles, computers, appliances of different types, and various other assemblies are known to be provided with metal inserts having internal threads so that another part can be held thereto by a bolt or screw engaged with the insert. It is also known to anchor a threaded stud in a plastic or other part so that another component can be held there on by a nut threaded onto the threads of the stud.
Various techniques are known for securing the anchored component, such as a threaded insert or stud, in the plastic or other part. Simple threaded engagement can be used, with threads on the outer surface of the insert or stud threaded into the component in which it is held. In a process known as heat-staking, a metal part, such as a threaded female insert or stud, is heated and pushed into the plastic component in which it is held, melting and fusing the inter-facing plastic surface on to the embedded portion of the insert or stud. Heat-staking can be performed relatively inexpensively. Ultrasonic insertion is also known whereby the part is vibrated ultrasonically and pushed into the receiving component. Ultrasonic insertion can be performed relatively quickly, but the process tends to be expensive. In a more simple mechanical process, the component to be anchored is provided with a knurled or other configured outer surface and is simply pushed into the receiving component. Mechanical insertion such as this can be performed quickly, but the machining process required to form the outer surface of the insert adds significantly to overall cost. Further, mechanical insertion tends to channel or direct the material of the anchoring component, and it has been difficult to achieve significant holding strength against pullout with push-in inserts. Further, to facilitate easy and rapid machining of inserts, it has been known to use expensive materials, such as brass, for inserts installed by all such methods. Knurls, undercuts and other such formations can be formed readily in brass; however, the costs of parts made of such materials are high.
Advantages can be obtained from providing an insert that can be driven readily while providing significant resistance to both pullout and rotation in the completed assembly. Further advantages are realized if the insert can be manufactured easily from inexpensive materials using simple and efficient manufacturing processes.